The ProfileGrid – User Profiles, Groups and Communities plugin for WordPress is vulnerable to privilege escalation via account takeover in all versions up to, and including, 5.9.9.5. This is due to the plugin not validating a `user_login` on registration forms that don't contain this parameter, and not properly handling the error messages. This makes it possible for unauthenticated attackers to change email address of user account with ID=1 (usually an administrator), and leverage that to reset the user's password and gain access to their account.